Grooved refractory pouring tube for metallurgical casting, assembly of refractory components, casting installation and process for repairing the surface of a refractory component

ABSTRACT

The object of the present invention is a refractory pouring tube including a contact face ( 15 ) capable of bearing against a contact face ( 11 ) of another refractory component ( 9 ), the said pouring tube being arranged to be displaced. The said pouring tube is characterised by the fact that its contact face ( 15 ) incorporates a cleaning groove ( 26, 27 ) delineated notably by a wall presenting an edge capable of exerting a scraping action, as the said pouring tube is displaced, at least partially on the determinate part of the contact face of the other refractory component. The cleaning groove makes it possible to preserve the integrity of the contact surface of the other refractory component and, consequently, the joint surface formed between the two components.

The present invention relates to a grooved refractory component and moreparticularly to a refractory pouring tube for metallurgical casting, andassembly of refractory components, a casting installation and a processfor repairing the contact face of a refractory component.

It is known that the casting of steel calls for the filling ofsuccessive metallurgical vessels, notably a ladle, a tundish and ingotmoulds, and that during its passage from one upper metallurgical vesselto a lower metallurgical vessel, the metal must as far as possible bekept out of all contact with the ambient air.

To this end, a pouring shroud or a submerged entry nozzle made ofrefractory material forms an extension to the pouring orifice of theupper vessel (respectively the ladle or tundish), and enters the moltenmetal present in the lower vessel (respectively the tundish or ingotmould), so that the molten metal passes from the ladle to the tundish orfrom the tundish to the ingot mould without ever being exposed to theambient air.

The pouring orifice of the upper vessel incorporates an inner nozzle inrefractory material, which opens below this vessel via a contact surfacedesigned to mate with a contact surface on the pouring shroud orsubmerged entry nozzle, thereby forming a joint face between these twocomponents.

Conventionally, a casting installation also includes means of regulatingthe flow of the molten metal. These means may consist of a stopper rodwhich enters the metal bath of the upper vessel opposite the pouringorifice and whose degree of immersion in the said metal bath determinesthe opening of the said pouring orifice. Alternatively, use may also bemade of a slide valve incorporating a set of refractory plates eachhaving an orifice. These plates are normally located between the innernozzle and the pouring shroud or the submerged entry nozzle. The degreeof alignment of the orifices in adjacent plates determines the flow ofmolten metal.

A continuous casting installation therefore includes numerous assembledrefractory components, the interfaces between which are formed bycontact surfaces that may be planar or non-planar, as indicated forexample in document U.S. Pat. No. 5,984,153.

It is known that the reductions in cross-section which occur along themolten metal pouring channel produce considerable negative pressurewhich can in turn lead to an induction of air.

The joint surface is generally effective in avoiding air inductionproblems, but it has been found that it has a tendency to deteriorate ateach replacement of the pouring shroud or submerged entry nozzle.

This replacement can be carried out, in a known manner, by positioning anew tube beside the tube to be replaced, then simultaneously moving thetwo tubes, allowing the new tube to displace the old one and take itsplace beneath the inner nozzle.

Prior to each replacement, the tundish pouring orifice is closed off,but it is possible for droplets of molten metal to remain at the jointsurface, at the interface between the pouring orifices of the tube andthe inner nozzle. These droplets, which solidify, are drawn into thejoint surface and cause more or less severe damage to the contact faceof the inner nozzle. As it is not possible to replace the inner nozzleduring casting, it is essential to preserve the integrity of this nozzleand in particular its lower contact face, so that the sealing tightnessof the joint surface formed with the contact face of the tube ismaintained for as long as possible and so that, consequently, thecasting operation need not be prematurely interrupted.

This problem is further exacerbated if the joint surface incorporates aninjection channel for a fluid, such as an inert gas, which may have thefunction both of preventing the ingress of ambient into the jointsurface and/or allowing the injection of a sealing agent into the jointsurface (as shown in documents WO 98/17420 and WO 98/17421, in order totreat the cracks which invariably propagate on the contact face of theinner nozzle and the score marks or scratches produced during tubechanges.

The droplets of metal trapped at the joint surface accumulate in theinjection channel and can cause it to become obstructed, therebyrendering it ineffective both in terms of preventing the admission ofambient air and in terms of the treatment of cracks and score marks orscratches.

When the tube is moved for the purposes of replacement, the extraneousmaterial obstructing the injection channel is sheared between the twocontact faces and spreads notably over part of the contact face of theinner nozzle.

The aim of the present invention is to remedy these problems in a simpleand economic manner.

The object of the present invention is a refractory pouring tube formingpart of a pouring channel and including at least one contact facecapable of bearing against a contact face of another refractorycomponent forming an adjacent portion of the pouring channel, the saidpouring tube being arranged to be displaced in a predefined trajectoryalong which its contact face slides and remains in bearing contactagainst the contact face of the other refractory component, the saidpouring tube being characterised in that its contact face incorporates acleaning groove delineated notably by a wall presenting an edge capableof exerting a scraping action, as the said pouring tube is displaced, atleast partially on the determinate part of the contact face of the otherrefractory component.

The pouring tube which is the object of the invention can be for examplea submerged entry nozzle or pouring shroud.

It is to be understood that, as it passes over the contact face of theother refractory component, the cleaning groove picks up all of theextraneous material accumulated on the latter, and notably any metaldroplets entrained during the relative movement of the two refractorycomponents.

Thus, for a refractory pouring tube whose replacement is effected bysimultaneous movement of the said pouring tube and its replacementpouring tube which displaces the former and takes its place in theworking position, the cleaning groove is found to be highly effective inclearing the joint surface of all dirt and extraneous matter such asmetal droplets entrained during the movement of the two refractorycomponents. Depending on whether the cleaning groove is located ahead ofor behind the pouring channel in relation to the direction of movementof the two components, the refractory pouring tube performs the scrapingaction for itself when it replaces a previous refractory pouring tube,or for a succeeding refractory pouring tube when the said refractorypouring tube is replaced by the next refractory pouring tube.

In a preferred embodiment of the invention, the cleaning groove ispositioned so that the cleaning edge is able to scrape the entirety ofthe determinate part of the contact face of the other refractorycomponent.

One possibility to achieve this purpose is for the cleaning groove to belocated behind the pouring channel in relation to the direction ofmovement of the refractory pouring tube, so that it passes over thedeterminate part of the contact face from its border with the pouringorifice up to its edge. In this case, the cleaning groove exerts itsaction not for the refractory pouring tube in which it is incorporated,but for its replacement.

According to a particular characteristic of the invention, the cleaninggroove is blind. Preferably, the cleaning groove should have a widthsuch that, when the groove is at the level of the pouring orifice (forexample when the tube is changed), it does not communicate with theinjection groove. Thus, if some molten metal remains at the interfacebetween the pouring orifices of the inner nozzle and the submerged entrynozzle, it will not reach the injection groove. Therefore, according toan advantageous characteristic of the invention, the cleaning groove isshorter than the minimum width between opposite sections of theinjection groove on either side of the pouring orifice at the level ofthe pouring orifice.

In a particular embodiment of the invention, the contact face of therefractory pouring tube incorporates a second groove essentiallyparallel to the cleaning groove.

This second groove may be located, relative to the first groove, on theother side of the pouring channel. It may even be symmetrical with thecleaning groove relative to the pouring channel, which is particularlyadvantageous if the refractory pouring tube can be used in two possiblepositions, by virtue of its own axial symmetry, as is the case withcertain pouring shrouds or submerged entry nozzles.

In a particular embodiment of the invention, the second groove partiallycovers an injection groove in the other refractory component defining aninjection channel.

The second groove then performs a different function from the cleaninggroove, namely that it allows a fluid injected into the injectionchannel to bypass a part of the said channel which may be blocked.

In order to avoid obstruction of the inlet or outlet of the injectionchannel, notably by a sealing agent carried by the injected fluid, thesecond groove may be formed so as to cover the opening of a deliveryline and, where appropriate, discharge line of the fluid injectionchannel.

In a particular embodiment of the invention, the refractory pouring tubeincorporates several grooves capable of scraping at least partially thedeterminate part of the contact face of the other refractory component.

The object of the present invention is also an assembly of refractorycomponents forming a pouring channel and each incorporating at least onecontact face bearing against the contact face of another adjacentrefractory component, characterised in that one of the refractorycomponents is a refractory pouring tube as described above.

In a particular embodiment of this assembly, the other refractorycomponent incorporates an injection groove which forms an injectionchannel with the contact face of the refractory pouring tubeincorporating the cleaning groove, into which injection channel emergesa delivery line and, where appropriate, discharge line provided in oneor more of the refractory components.

The object of the present invention is also a casting installationincluding an upper metallurgical vessel and a lower metallurgical vesselconnected by a pouring channel defined notably by an assembly ofrefractory components as described above.

According to a particular characteristic, the assembly of refractorycomponents is equipped with an injection channel and the castinginstallation includes a fluid source connected to the delivery line ofthe fluid injection channel.

According to an additional characteristic, the casting installation alsoincludes a means of injecting a sealing agent, for example powderedgraphite, into the fluid.

A further object of the present invention is a process for repairing thecontact face of a refractory component forming part of a pouringchannel, the said contact face being capable of serving as a bearingsurface for a contact face of another refractory component (i.e. apouring tube) forming an adjacent part of the pouring channel, the saidother component being arranged to be displaced in a pre-definedtrajectory along which its contact face slides and remains in bearingcontact against the contact face to be repaired, whilst the portion ofthe pouring channel formed by the said other component defines adeterminate part of the contact face to be repaired, the process beingcharacterised in that, as the pouring tube is displaced, the determinatepart of the contact face to be repaired is scraped at least partially bythe cleaning groove formed on the contact face of the said pouring tubeand delineated notably by a wall presenting an edge suitably shaped forthis purpose.

In order to better explain the invention, a mode of implementation givenby way of example which does not limit the scope of the invention willbe described below with reference to the attached diagram in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an axial cross-section of an inner nozzle of a tundish and asubmerged entry nozzle,

FIG. 2 is a view on the underside of the contact face of the innernozzle,

FIG. 3 is an upper view on the contact face of the submerged entrynozzle,

FIG. 4 shows the superimposed contact faces of the inner nozzle and thesubmerged entry nozzle,

FIG. 5 is a view similar to FIG. 1 showing a slide valve interposedbetween the inner nozzle and the submerged entry nozzle,

FIG. 6 is a view on the underside of the fixed bottom plate of the slidevalve.

FIG. 1 shows the bottom wall 1 of a tundish, in a region surrounding oneof its pouring orifices 2.

The tundish is fitted with a device 3 for changing the tube 4 whichincludes a mounting plate 5 integral with the bottom wall of thetundish, guide-rails 6 accommodating the collars 7 of two submergedentry nozzles which are thus held in proximity to the mounting plate 5,and a cylinder 8 to push the two submerged entry nozzles 4 in theguide-rails.

The pouring orifice 2 of the tundish is lined with an inner nozzle 9made of refractory material, which passes through the mounting plate 5and bears on the lower face of the latter by means of a flat contactface 11.

The guide-rails 6 hold the two submerged entry nozzles 4 against thecontact face 11 of the inner nozzle at an elevated pressure equivalentto a weight of several tonnes.

In FIG. 1, the submerged entry nozzle 4 on the right is the one whichforms, in conjunction with the inner nozzle 9, a portion of the pouringchannel 12 for the molten metal. The nozzle to the left is the one whichhas just been replaced by moving in the guide-rails 6 under the actionof the cylinder 8.

A stopper rod 10 can be applied against the upper orifice 13 of theinner nozzle to regulate the metal flow or to interrupt pouring, notablyto allow replacement of the submerged entry nozzle.

FIG. 2 illustrates the contact face 11 of the inner nozzle.

The pouring orifice has an elongated cross-section oriented in adirection 17 which is parallel to the guide-rails 6, i.e. the directionin which the submerged entry nozzles are moved when the older of the twonozzles is being replaced.

Around the pouring orifice, the contact face incorporates an injectiongroove 18 in the form of a three-quarter partial circle extending intostraight sections of which the ends 20 are close together but which arenot in communication with each other. One end 20 communicates with theoutlet 21 of a delivery line, or respectively a discharge line, formedin the inner nozzle 9.

In FIG. 3, it can be seen that each submerged entry nozzle 4 delineatesa portion 24 of elongated transverse cross-section (in direction 17) ofthe pouring channel, and that its collar 7 is rectangular in shape toenable it to be guided in the guide-rails 6 of the submerged entrynozzle changer 3.

The contact face 15 of each submerged entry nozzle, formed by the upperface (according to the orientation in FIG. 1) of its collar 7, coversthe injection groove 18 of the inner nozzle 9 when the submerged entrynozzle 4 is in the working position, and thus forms an injection channelfor fluid and/or sealing agent to prevent the admission of ambient airinto the pouring channel and/or to prevent damage to the refractorymaterial constituting the inner nozzle around its cracks or score marks25.

When the submerged entry nozzle 4 is replaced, the contact faces 15 ofthe two submerged entry nozzles slide in the direction 17 against thecontact face 11 of the inner nozzle.

Droplets of molten metal present around the pouring channel, at theinterface between the inner nozzle and the submerged entry nozzle, i.e.at the joint surface, are entrained by the submerged entry nozzle into adeterminate part 22 of the contact face of the inner nozzle locatedbehind the pouring orifice in the direction of movement of the submergedentry nozzles.

These droplets of metal have two deleterious effects.

Firstly, they foul this determinate part 22 by preventing proper surfacecontact to be established between the contact faces of the inner nozzleand the submerged entry nozzle.

The second deleterious effect is that they accumulate in a portion 23(marked by a thick line in FIG. 2) of the injection groove correspondingto the intersection of the said injection groove with the saiddeterminate part 22, and give rise to blockage of the injection channelduring subsequent use of the replacement submerged entry nozzle.

The blockage which occurs during the use of the nozzle as it is beingreplaced is itself a damaging factor, as the extraneous materialconstituting the obstruction is sheared between the contact faces of theinner nozzle and the submerged entry nozzle, and is entrained into thedeterminate part 22.

Two cleaning grooves 26 and 27 are formed in the contact face 15 of eachsubmerged entry nozzle 4. Each of these is delimited by an edge whoseform is determined so as to scrape the contact face of the inner nozzleand to remove all extraneous material which is trapped there. The personskilled in the art can determine a more or less sharp configuration forthis edge to achieve optimum scraping.

The cleaning grooves are positioned so as to scrape at least partially,as the submerged entry nozzle is displaced in the guide-rails, thedeterminate part 22 of the contact face of the inner nozzle.

In the example shown, the two cleaning grooves 26 and 27 are centrallysymmetrical about the centre 28 of the contact face, which essentiallycoincides with the centre of the transverse cross-section of the pouringchannel, by the fact that each submerged entry nozzle can be used in thetwo possible positions of engagement of its rectangular collar 7 in theguide-rails 6.

In reality, only the cleaning groove 26 located ahead of the pouringchannel performs the cleaning function on the contact face 11 of theinner nozzle, for the replacement nozzle.

In effect, when the cleaning groove 26 of the submerged entry nozzlebeing replaced arrives at the vertical of the determinate part 22 of thecontact face 11 of the inner nozzle, it scrapes it and leaves behind aclean surface ensuring good quality contact between the inner nozzle andthe contact face of the replacement submerged entry nozzle.

If, despite the scraping action performed by the submerged entry nozzlewhich has been replaced, the portion 23 of the injection groove becomesblocked during use of the replacement submerged entry nozzle, the fluiddelivered into the injection channel can bypass the blocked section ofthe injection groove 18 by circulating through the second groove 27(which, in the position that it occupies, does not perform a cleaningfunction, as already indicated) of the submerged entry nozzle. Thesecond groove 27 communicates with the injection groove 18 on both sidesof its obstructed section 23. The fluid can thus reach the rest of theinjection channel to act as prescribed against the ingress of air and/orto treat cracks.

Beyond its circular section covering the determinate part 23 of theinjection groove, the second groove 27 extends into a straight lengthwhich covers the straight section of the injection groove.

Thus, the second groove clears not only that part of the injectiongroove liable to be obstructed, but it also clears the opening 21 of itsdelivery line, so that the sealing agent, if it is carried by the fluid,has a sufficient volume upon its arrival in the injection channel not tocongeal and block the channel at its inlet.

The slide valve 30 in FIG. 5 is interposed between the inner nozzle 9and the submerged entry nozzle 4 described previously.

This slide valve 30 is composed of a fixed upper plate 31, anintermediate mobile plate 32, and a fixed bottom plate 33.

As explained above, the inner nozzle 9 can incorporate an injectiongroove. In this case, the injection channel is formed with the upperface (relative to FIG. 4) of the fixed upper plate 31.

Other joint surfaces are formed between the fixed plates 31, 33 and themobile plate 32 of the slide valve. As is known, other injectionchannels can be made in these joint surfaces to prevent the admission ofair.

A joint surface is present between the fixed bottom plate 33 and thesubmerged entry nozzle 4 which poses the same risks of damage as thatdescribed in reference to FIGS. 1 to 4, by the fact that replacements ofthe submerged entry nozzle 4 cause friction and risks of obstruction ofan injection groove 34 formed in the lower face (relative to FIG. 4) ofthe fixed bottom plate 33 which in conjunction with the contact face ofthe submerged entry nozzle forms a fluid injection channel.

By reason of this risk, the cleaning grooves 26 and 27 of a submergedentry nozzle identical to that in FIG. 3 fulfil the same functions withregard to the fixed bottom plate as in respect of the inner nozzle inFIG. 1.

Although the cleaning grooves have been described for submerged entrynozzles with reference to a flat joint surface at the outlet of atundish, it is to be understood that the invention applies to anyinterface (planar or non-planar) between two refractory componentsforming a fluid injection channel between them.

With regard to FIG. 6, reference will be made mutatis mutandis to thedescription of FIG. 2, and the reference 34 designates an injectiongroove formed in the lower face (relative to FIG. 5) of the fixed bottomplate.

1. tundish bottom wall

2. pouring orifice

3. tube changing device

4. submerged entry nozzle

5. mounting plate

6. guide-rails

7. tube collar

8. cylinder

9. inner nozzle

10. stopper rod

11. inner nozzle contact face

12. part of the pouring channel

13. upper orifice of the inner nozzle

15. submerged entry nozzle contact face

17. direction X

18. injection groove

20. groove ends

21. opening of a delivery line or discharge line, respectively

22. determinate part of the contact face of the inner nozzle

23. obstructed portion of the injection groove

24. portion of elongated transverse cross-section in direction X of thepouring channel of the submerged entry nozzle

25. cracks, score marks and scratches on the inner nozzle

26. cleaning groove

27. second groove

28. centre of the contact face of the submerged entry nozzle

30. slide valve

31. fixed upper plate

32. mobile intermediate plate

33. fixed bottom plate

34. injection groove formed in the lower face (relative to FIG. 5) ofthe fixed bottom plate

What is claimed is:
 1. A refractory pouring tube defining a firstportion of a pouring channel and comprising a first contact face adaptedto be displaced relative to a second contact face of a second refractorycomponent defining an adjacent portion of the pouring channel, wherebydisplacement comprises sliding the first contact face relative to whilemaintaining bearing contact against the second contact face and thefirst and second refractory components define an injection groovesubstantially encircling the pouring channel and having a determinatepart behind the pouring channel relative to the displacement, the firstcontact face comprises a cleaning groove and a second groove, thecleaning groove presenting an edge adapted to scrape the second contactface as the pouring tube is displaced, the second groove is essentiallyparallel to the cleaning groove, and the second groove and the cleaninggroove are on opposite sides of the pouring channel.
 2. The refractorypouring tube of claim 1, wherein the cleaning groove is adapted toscrape the determinate part.
 3. The refractory pouring tube of claim 1,wherein the pouring tube comprises a submerged entry nozzle.
 4. Therefractory pouring tube of claim 1, wherein the cleaning groovecomprises a blind passageway.
 5. A refractory pouring tube defining afirst portion of a pouring channel and comprising a first contact faceadapted to be displaced relative to a second contact face of a secondrefractory component defining an adjacent portion of the pouringchannel, whereby displacement comprises sliding the first contact facerelative to while maintaining bearing contact against the second contactface and the first and second refractory components define an injectiongroove substantially encircling the pouring channel and having adeterminate part behind the pouring channel relative to thedisplacement, the first contact face comprises a cleaning groove and asecond groove, the cleaning groove presenting an edge adapted to scrapethe second contact face as the pouring tube is displaced, the secondgroove is essentially parallel to the cleaning groove and the secondgroove and the cleaning groove are symmetrical relative to the pouringchannel.
 6. The refractory pouring tube of claim 1, wherein the secondgroove is adapted to at least partially cover the injection groove,thereby forming an injection channel.
 7. The refractory pouring tube ofclaim 1, wherein the injection groove includes an opening, and thesecond groove is adapted to cover the opening.
 8. The refractory pouringtube of claim 1, wherein the pouring tube comprises a plurality ofcleaning grooves.